This proposal is to identify a ciliated model invertebrate that would be suitable for a future genome sequencing project. The investigators will identify an annelid from among a subset of those with a history of laboratory culture using a number of criteria, such as small size and ease of culture, potential for genetic manipulation, easily observable embryonic development, genome size less than 10exp9 bp, and slowly evolving genes. Once an annelid is selected, they will construct a cDNA library from adult annelids to demonstrate their ability to carry out a future annelid cDNA project, which could be the foundation for an annelid genome project. There are three good reasons to pursue a new invertebrate model: (1) Approximately 50 percent of the diversity of invertebrates is not being sampled in current genome projects. It has only been recently been recognized that arthropods (Drosophila) and nematodes (Caenorhabditis) are closely related, and as a result that much bilateral animal biology is not being sampled. An annelid project would fill in the missing gap and sample the remaining invertebrate diversity. (2) Knowledge of annelid gene sequences will facilitate the identification of less conserved orthologs among humans, Drosophila, and Caenorhabditis. The recent findings that Drosophila and Caenorhabditis genes are rapidly evolving, whereas annelid genes are slowly evolving, means that similarity scores between orthologous human and fly/nematode genes tend to be lower than those between human and annelid genes. Use of annelid cDNAs will allow one to more accurately identify Drosophila and Caenorhabditis orthologs. (3) Because many chronic human diseases are related to defective cilia, and since Drosophila and Caenorhabditis both lack motile cilia, there is a need for a model organism having motile cilia (annelids have motile cilia).